Milk composition and feed intake in dairy cows selected for high or low milk fat percentage

Dairy cows, selected for high (HFI) or low (LFI) milk fat percentage but eq ual fat-corrected milk (FCM) yield, were studied regarding feed intake, mil k production, milk composition, body weight and body condition. Forty-eight Swedish Red and Whits breed primiparous and multiparous cows from the sele ction lines, fed the same diet and milked twice a day, were followed during one lactation. The selection lines produced on average the same total amou nt of FCM, milk fat and protein. The LFI cows yielded greater milk volume a nd more total amount of lactose, but the HFI cows had higher percentages of milk fat, total protein and casein. Milli fat from the LFI cows had a smal ler proportion of palmitic acid and larger proportions of linoleic and lino lenic acids, compared with the HFI cows. No differences in body weight were found, but the LFI cows had more subcutaneous fat over the longissimus dor si muscle, and tended to have a higher feed intake than the HFI cows. The s tudy indicates that the selection lines differ in metabolism and partitioni ng of nutrients. (C) 1999 Elsevier Science BN. All rights reserved.